FACTORS CONTRIBUTING TO THE INCREASED CESAREAN BIRTH-RATE IN OLDER PARTURIENT WOMEN

OBJECTIVE: Our purpose was to determine factors contributing to the in creased use of cesarean section in patients greater-than-or-equal-to 3 5 years old. STUDY DESIGN: Data were collected prospectively on nullip arous patients in spontaneous labor with term, singleton pregnancies a nd vertex presentations. Criteria for the diagnosis of labor were stan dardized: regular, painful uterine contractions at least once every 5 minutes in the presence of either complete cervical effacement or spon taneous rupture of membranes. The labors of women greater-than-or-equa l-to 35 years old (n = 74) were compared with those of women 20 to 29 years old (n = 275). RESULTS: The cesarean section rate was significan tly greater for patients greater-than-or-equal-to 35 years old (21.6% vs 10.2%, odds ratio 2.4, 95% confidence interval 1.2 to 5.1). Mean bi rth weights were similar in the two groups, but when birth weight was greater-than-or-equal-to 3600 gm patients greater-than-or-equal-to 35 years old were more likely to be delivered by cesarean section (36.7% vs 12.2%, odds ratio 4.0, 95% confidence interval 1.4 to 11.9). There were no differences between the two age groups in physician factors th at could explain the disparate rates of cesarean delivery. Indeed, of patients delivered vaginally the older parturients received oxytocin f or longer duration (6.4 +/- 2.6 vs 5.0 +/- 3.1 hours, p < 0.005) and a t higher maximum doses (12.4 +/- 6.1 vs 9.8 +/- 6.2 mU, p < 0.05). Aft er controlling for potentially confounding variables with multiple log istic regression analysis, maternal age (R = 0.125, p < 0.005), birth weight (R = 0.196, p < 0.001), the need for oxytocin (R - 0.210, p < 0 .001), and epidural anesthesia (R = 0.195, p < 0.001) were found to be independently associated with the increased rate of cesarean section. CONCLUSION: We could not identify any controllable physician factors affecting the rate of cesarean section in patients greater-than-or-equ al-to 35 years old. The increased oxytocin requirements and the incide nce of dystocia with birth weight greater-than-or-equal-to 3600 gm sug gest that maternal and fetal characteristics contribute to the increas ed frequency of cesarean section ir older parturients.